A competitive landscape -- including surging Android tablet shipments and robust demand for Apple's new iPad mini -- has led IDC to increase its 2012 forecast for the worldwide tablet market to 122.3 million, up from its previous forecast of 117.1 million units.

IDC said it boosted its forecast for global tablet sales for 2012 to 122.3 million, from 117.1 million, in large part due to demand for Android tablets and the new iPad mini.

IDC also raised its 2013 forecast number to 172.4 million, up from 165.9 million and said shipments by 2016 worldwide shipments should reach 282.7 million.

"Tablets continue to captivate consumers, and as the market shifts toward smaller, more mobile screen sizes and lower prices points, we expect demand to accelerate in the fourth quarter and beyond," said Tom Mainelli, research director, Tablets at IDC. "Android tablets are gaining traction in the market thanks to solid products from Google, Amazon, Samsung, and others. And Apple's November iPad mini launch, along with its surprise refresh of the full-sized iPad, positions the company well for a strong holiday season."

IDC now expects Android's worldwide tablet share to increase to 42.7 percent for 2012 from 39.8 percent in 2011. Apple's share is expected to slip to 53.8 percent from 56.3 percent in 2011.

"The breadth and depth of Android has taken full effect on the tablet market as it has for the smartphone space," said Ryan Reith, an IDC analyst.

"Android tablet shipments will certainly act as the catalyst for growth in the low-cost segment in emerging markets given the platform's low barrier to entry on manufacturing. At the same time, top-tier companies like Samsung, Lenovo, and ASUS are all launching Android tablets with comparable to premium products, but offered at much lower price points."

IDC also updated its operating system splits for the year to reflect Android's growing strength in the tablet market. IDC now expects Android's worldwide tablet share to increase from 39.8% in 2011 to 42.7% for the full year of 2012. During that same time Apple's share will slip from 56.3% in 2011 to 53.8% in 2012. Long term, IDC predicts Windows-based tablets (including Windows 8 and Windows RT) will grab share from both iOS and Android, growing from 1% of the market in 2011 to 2.9% in 2012, on its way to 10.2% in 2016.

IDC predicts Windows-based tablets, including new devices from Microsoft and others, will gain share from both iOS and Android, growing from one percent of the market in 2011 to 2.9 percent in 2012 and 10.2 percent in 2016.